Remove declaration of non-existent method

CommitToStorage was removed in #20010.

Signed-off-by: Adrian Gielniewski <adrian.gielniewski@nordicsemi.no>

Author: adigie

src/app/FailSafeContext.h

@@ -152,7 +152,6 @@ class FailSafeContext
     }
 
     void FailSafeTimerExpired();
-    CHIP_ERROR CommitToStorage();
 };
 
 } // namespace app